A wealth of astrophysical research supports the existence of dark matter in the universe, yet the exact identity and nature of this unknown particle remain elusive. The Weakly Interacting Massive Particle (WIMP), one of the most promising dark matter candidates, is thought to interact with Standard Model particles only through the gravitational and weak nuclear forces. The Large Underground Xenon (LUX) experiment is one of a large number of experiments that seek to detect WIMPs through their rare but discernible scatters off of target nuclei. Specifically, LUX is a 370-kg dual-phase xenon-based time projection chamber (TPC) that operates by detecting light and ionization signals from particles incident upon a xenon target. The first part of this dissertation details the design of the LUX experiment and describes several novel hardware subsystems that allow LUX to detect extremely rare events with high precision. With the 2013 release of the world's first sub-zeptobarn spin-independent WIMP-nucleon cross section limit, the LUX (Large Underground Xenon) experiment has emerged as a frontrunner in the field of dark matter direct detection.
However, tension between experiments and the absence of a definitive positive detection suggest it would be prudent to search for answers outside the standard spin-independent/spin-dependent analyses. hi particular, the standard analyses neglect momentum- and velocity-dependent interactions on the grounds that WIMP-nucleus collisions are nonrelativistic. At the parton level, this is not always the case, and moreover, models exist in which the standard spin-independent and spin-dependent interactions are subdominant to new kinds of interactions. Recent theoretical work has identified a complete set of 14 possible independent WIMP-nucleon interactions using basic symmetries and an effective field theory formulation. These interactions produce not only spin-independent and spin-dependent nuclear responses but also novel nuclear responses such as angular-momentum-dependent and spin-orbit couplings. In the second portion of this dissertation we report on the extension of the LUX analysis to search for all 14 of these operators, we comment on the possible suppression of event rates due to operator interference, and we show that under this new framework, LUX again exhibits world-leading sensitivity.
|Advisor:||McKinsey, Daniel N.|
|School Location:||United States -- Connecticut|
|Source:||DAI-B 78/01(E), Dissertation Abstracts International|
|Keywords:||Astroparticle Physics, Dark Matter, Direct Detection, Effective Field Theory, Liquid Xenon, WIMP|
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